A variety of flavorants have been developed and proposed for incorporation into tobacco products. Illustrative of such tobacco flavorants are those described in U.S. Pat. Nos. 3,580,259; 3,625,224; 3,722,516; 3,750,674; 3,879,425; 3,881,025; 3,884,247; 3,890,981; 3,903,900; 3,914,451; 3,915,175; 3,920,027; 3,924,644; 3,937,228; 3,943,943; 3,586,387; 4,379,754; and the like.
U.S. Pat. No. 4,036,237 describes smoking compositions which contain an aromatic beta-hydroxy ester flavorant such as ethyl 2,2-dimethyl-3-hydroxy-3-phenylpropionate, which volatilizes under smoking conditions.
U.S. Pat. No. 4,312,368 describes smoking compositions which contain a heterocyclic-hydroxy-substituted carboxylate flavorant-release additive such as ethyl 2-(2-butyl)-3-hydroxy-3-methyl-3-(3-pyridyl)propionate. Under smoking conditions this additive pyrolyzes into 3-acetylpyridine and ethyl .beta.-methylvalerate flavorants.
J. C. Leffingwell et al "Tobacco Flavoring For Smoking Products" (R. J. Reynolds publication, 1972) includes 1,2-diketone compounds in a listing of desirable flavorants for smoking compositions. Aliphatic 1,2-diketones such as 2,3-butanedione, 2,3-pentanedione, 2,3-hexanedione and 2,3-heptanedione are described as having a buttery, nutty aroma.
Other 1,2-diketones such as 1-phenyl-1,2-propanedione have a sweet balsamic aroma. U.S. Pat. No. 3,903,900 discloses cyclic 1,2-diketone tobacco flavorants such as 3-methyl-1,2-cyclopentanedione which has a strong caramel-spicy aroma.
A difficulty encountered with 1,2-diketone type of tobacco flavorants is the problem of a relatively low boiling point, which results in flavorant evaporation loss on prolonged storage of the flavored tobacco compositions. Thus, 2,3-butanedione as a component of tobacco smoke is characterized by a distinct buttery sweet taste and a desirable smoothing effect in smoke. However, a boiling point of 88.degree. C. precludes the utility of this 1,2-diketone as a tobacco composition flavorant because of evaporation loss.
There is continuing research effort to develop improved low delivery smoking compositions which generate mainstream smoke with flavorant-enhanced taste and character under smoking conditions.
Accordingly, it is an object of this invention to provide smoking compositions having incorporated therein a flavorant component which is characterized by lack of mobility and/or volatility at ambient temperature.
It is another object of this invention to provide smoking tobacco compositions having incorporated therein a flavorant-release composition which under normal smoking conditions imparts improved flavor to mainstream smoke and improved aroma to sidestream smoke.
It is a further object of this invention to provide novel .beta.-hydroxy-.gamma.-ketoester compositions which are adapted to be incorporated into tobacco compositions, and which under normal smoking conditions release a 1,2-diketone type of volatile flavorant into cigarette smoke.
Other objects and advantages of the present invention shall become apparent from the following description and examples.